The present invention relates to a projection type image display apparatus.
In a prior art, a projection optic system (FIG. 8) using one free-form-surface mirror and two free-form-surface lenses and technique (FIG. 9) in which the two free-form-surface lenses thereof are moved in an interlocked relationship with each other for focusing are known (refer to JP-A-2010-72374 and JP-A-2009-109867).
FIG. 10A is a schematic diagram which extracts free-form-surface lenses functioning as focusing lenses and a fixed lens disposed before the lenses and FIG. 10B is a schematic diagram illustrating movement loci of the free-form-surface lenses functioning as focusing lenses, that is, a cam diagram. In FIGS. 10A and 10B, the smaller an image projected onto a screen is, the more the focusing lenses are moved to an image plane side. Further, a movement amount of the focusing lens on the image plane side is larger than a movement amount of the focusing lens on an image display element side.